Dynamic sealing

ABSTRACT

A dual seal accommodates radial and axial movement, and accommodates positive and negative pressure differentials, when in sealing engagement about a rotating shaft.

TECHNICAL FIELD

This invention relates to seals, particularly to dual seals.

BACKGROUND

Seals are employed in a wide variety of mechanical apparatuses toprovide pressure-tight and fluid-tight sealing. The seal is oftenpositioned about a rotating shaft extending from a stationary housing.The seal may be bolted to the housing at the shaft exit, to restrict theloss of pressurized fluid from the housing. In other situations, theseal may be designed or adjusted to permit a controlled flow of fluid.

SUMMARY

A dual seal as described herein accommodates radial and axial movement,and accommodates positive and negative pressure differentials, when insealing engagement about a rotating shaft.

In some embodiments, dual seals as illustrated herein include a sealingelement, a balancing element, and an adapter disposed within an interiorcavity of a gland housing. The gland housing can provide a bidirectionalseal between an interior region of a vessel and a barrier fluid cavity.The sealing element can compensate for lateral movement of the shaft,and/or for variations in shaft radius, by moving radially relative to anaxis of the seal. Thermal effects can cause axial expansion orcontraction of the sealing element relative to the gland housing, e.g.when the sealing element and the gland housing are made of materialswith different coefficients of thermal expansion. The balancing elementcan move axially to compensate for such thermal expansion or contractionof the sealing element. The seal can be configured such that axialmovement of the balancing element maintains sealing contact between thebalancing element and the sealing element, e.g., while continuing toallow the radial movement of the sealing element, as the sealing elementexpands and contracts.

In one aspect, seals configured to extend circumferentially about ashaft include: a housing defining an interior cavity open towards acentral axis of the seal; a sealing element configured to move radiallywithin the interior cavity in a manner to maintain sealing contact, thesealing element disposed within the interior cavity of the housing; afirst seal disposed between the sealing element and the housing, thefirst seal maintaining sealing contact to limit fluid flow between thesealing element and the housing; a first element configured to moveaxially within the interior cavity in a manner to maintain sealingcontact, the first element disposed within the interior cavity of thehousing; a second seal disposed between the first element and thesealing element, the second seal maintaining sealing contact to limitfluid flow between the sealing element and the first element duringradial motion of the sealing element relative to the first element; abiasing member disposed in contact with the first element, the biasingmember configured to bias the first element towards sealing contact withthe sealing element such that first element and the second seal maintainsealing contact during axial movement of an end face of the sealingelement; and a third seal disposed between the first element and thehousing, the third seal maintaining sealing contact to limit fluid flowbetween the housing and the first element. Embodiments can include oneor more of the following features.

In some embodiments, seals also include a second element disposedbetween the first element and the housing and the third seal is disposedin a third seal cavity mutually defined by the first element and thesecond element. In some cases, the third seal is disposed to limit fluidflow between a first portion of the cavity in fluid communication with afirst fluid reservoir at a first pressure and a second portion of thecavity in fluid communication with a second fluid reservoir at a secondpressure.

In some cases, a pressure differential between the first pressure andthe second pressure, taken across the third seal, biases the firstelement towards the sealing element when the first pressure isrelatively greater (i.e., when the first pressure is greater than thesecond pressure) and also biases the first element towards the sealingelement when the second pressure is relatively greater (i.e., when thesecond pressure is greater than the first pressure). The third seal canbe operable to move axially in the third seal cavity in response to apressure differential between the first pressure and the secondpressure. For example, the third seal can be operable to move axially inthe third seal cavity in response to the pressure differential with thethird seal being urged toward a first position when the first pressureis relatively greater and toward a second position when the firstpressure is relatively less.

In some embodiments, the third seal comprises an o-ring.

In some embodiments, the sealing element includes: a sealing elementbody; a plurality of first land protrusions integrally formed with andextending from the sealing element body; and a plurality of second lipprotrusions integrally formed with and extending from the sealingelement body. The second lip protrusions can be biased towards aposition in which the second lip protrusions extend relatively furtherfrom the body than the first land protrusions. In some cases, eachsecond protrusion defines a resilient ridge positioned for deflection bycontact with an annular member inserted into the sealing member. In somecases, the second lip protrusions are arranged in pairs with a firstpair of the second lip protrusions having tips deflected towards asecond pair of the second lip protrusions, the second pair ofprotrusions having tips deflected towards the first pair of the secondlip protrusions, and a third pair of second lip protrusions having tipsdeflected away from the first pair and second pair of second lipprotrusions.

In some cases, a first end of the annular member defines a first beveledsurface disposed between a radially extending end surface of the annularmember and a second beveled surface, the second beveled surface disposedbetween the first beveled surface and an axially extending outer surfaceof the annular member. The first beveled surface can extend at an anglebetween 155 and 165 degrees relative to the axially extending outersurface of the annular member and the second beveled surface can extendat an angle between 165 and 175 degrees relative to the axiallyextending outer surface of the annular member.

In some cases, the first land protrusions are relatively less flexiblethan the second lip protrusions.

In some embodiments, seals also include a pin extending from the housinginto a bore defined in the sealing element to limit rotation of thesealing element relative to the housing while allowing radial motion ofthe sealing element within the housing.

In some embodiments, the seal can comprise a split seal.

In another aspect, seals configured to extend circumferentially about ashaft include: an annular housing defining a cavity open towards acentral axis of the seal; and a sealing element disposed at leastpartially within the cavity, the sealing element moveable radiallywithin the cavity; wherein the sealing element comprises: a sealingelement body; a plurality of first land protrusions integrally formedwith and extending from the sealing element body; and a plurality ofsecond lip protrusions integrally formed with and extending from thesealing element body, the second lip protrusions being biased towards aposition to extend relatively further from the sealing element body thanthe first land protrusions. Embodiments can include one or more of thefollowing features.

In some embodiments, each of the second lip protrusions defines aresilient ridge, positioned for deflection by contact with an annularmember inserted into the sealing member. In some cases, the second lipprotrusions are arranged in pairs with a first pair of the second lipprotrusions having tips deflected towards a second pair of the secondlip protrusions, the second pair of second lip protrusions having tipsdeflected towards the first pair of the second lip protrusions, and athird pair of second lip protrusions having tips deflected away from thefirst pair and the second pair of second lip protrusions.

In some embodiments, seals also include a pin extending from the housinginto a bore defined in the sealing element to limit rotation of thesealing element relative to the housing while allowing radial motion ofthe sealing element within the housing.

In another aspect, methods of sealing about a rotating shaft include:positioning a seal housing about the shaft; disposing a circumferentialsealing element in a seal housing cavity open towards the shaft, withthe sealing element mounted to maintain sealing contact during radialmovement of the sealing element within the cavity, while limiting fluidflow along an outer surface of the shaft; and disposing acircumferential first element in the seal housing cavity, with the firstelement mounted to maintain sealing contact during axial movement of thefirst element within the cavity, while limiting fluid flow along anouter surface of the shaft. Embodiments can include one or more of thefollowing features.

In some embodiments, methods also include biasing the first elementtowards sealing contact with the sealing element using a biasing member.

In some embodiments, methods also include: providing a first pair of lipseals and a second pair of lip seals integrally formed with andextending from a base of the sealing element; and applying a pressurizedfluid between the first and second pair of lip seals.

In some embodiments, methods also include: providing the sealing elementwith an annular body and multiple lip seals integrally formed with andextending radially inward from the body. In some cases, methods alsoinclude: engaging one of the lip seals with a first beveled surface ofan annular member disposed about the shaft; and bending the one of thelip seals towards a direction from which the shaft is inserted throughthe sealing element.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a dual seal.

FIGS. 2A and 2B are a cross-sectional view of the seal of FIG. 1 mountedabout a shaft with barrier fluid pressure greater than process pressureand an enlarged view of a portion of the seal shown in FIG. 2A,respectively.

FIG. 2C is a cross-sectional views of the seal of FIG. 1 mounted about ashaft with barrier fluid pressure less than process pressure,respectively.

FIGS. 3A and 3B are cross-sectional views of the seal of FIG. 1illustrating seal compensation for radial motion of the shaft.

FIGS. 4A and 4B are cross-sectional views of the seal of FIG. 1illustrating seal compensation for thermal effects on seal components.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

In FIG. 1, a seal 10 is configured to be positioned about a rotatingshaft (not shown). Seal 10 includes a housing clamp 14 and a glandhousing 18 which together form an annular mount to position and supportother components of seal 10. Housing clamp 14 can be used to attach seal10 to a surface (e.g., the wall of a process vessel) through which theshaft extends. Housing clamp 14 engages, and holds in position, glandhousing 18. Gland housing 18 defines an interior cavity 20 open towardsa central axis 24 of seal 10. (As used herein, the term “axially”indicates a direction generally along the axis 24 of seal 10 and theterm “radially” indicates a direction generally perpendicular to axis 24of seal 10. Similarly, “inward” and “inner” are used to indicate towardsor generally closer to the axis and “outward” and “outer” are used toindicate away from or generally further from the axis.)

Seal 10 also includes a sealing element, a balancing element, and anadapter disposed within interior cavity 20, as discussed below. A lockring 22 is configured to hold a seal sleeve 26 in position about theshaft with seal sleeve 26 extending into an interior cavity 20 definedby housing clamp 14 and gland housing 18. Seal sleeve 26 and a lock ring22 are mounted upon and rotate with the shaft.

In FIGS. 2A, 2B, and 2C, seal 10 is mounted to a wall 30 of a processvessel to limit fluid flow along shaft 34 which extends through wall 30of the process vessel. Sealing element 38, balancing element 42, andadapter 46 are disposed within interior cavity 20 defined by glandhousing 18. Gland housing 18 can provide a bidirectional seal between aninterior region 54 of the process vessel and a barrier fluid cavity 50.Barrier fluid cavity 50 is defined by gland housing 18, sealing element38, balancing element 42, and adapter 46. Sealing element 38 cancompensate for lateral movement of shaft 34, and/or for variations inshaft radius, by moving radially relative to axis 24 of seal 10. Thermaleffects can cause axial expansion or contraction of sealing element 38relative to gland housing 18, e.g. when sealing element 38 and glandhousing 18 are made of materials with different coefficients of thermalexpansion. Balancing element 42 can move axially to compensate for suchthermal expansion or contraction of sealing element 38. Seal 10 can beconfigured such that axial movement of balancing element 42 maintainssealing contact between balancing element 42 and sealing element 38,e.g., while continuing to allow the radial movement of sealing element38, as sealing element 38 expands and contracts.

As used herein, sealing contact is used to indicate proximity betweentwo objects that limits the flow of a fluid between the objects. Forexample, two objects can be in sealing contact without touching eachother (e.g., the two objects may be separated by a layer of lubricant orof the fluid whose flow is being limited). In another example, fluid mayflow at a desired rate or seep between two objects in sealing contact.

As mentioned above, seal 10 is mounted to wall 30 of the process vesselby housing clamp 30. Bolts 58 inserted through bores 62 in housing clampare threaded into mounting bores 66 machined into wall 30 of the processvessel. A counterbore region 70 machined into wall 30 of the processvessel receives a first end 78 of housing clamp 14. Engagement betweencounterbore region 70 and housing clamp 14 can help provide structuralstability and can help set the position of seal 10 relative to anopening 74 in wall 30 through which shaft 34 extends. A second end 82 ofhousing clamp 14 includes a projection 86 that extends radially inward.Housing clamp 14 can be formed (e.g., machined) out of durable,structurally stable materials such as stainless steels and other metalsand alloys.

Gland housing 18 includes a first portion 114 adjacent to wall 30 of theprocess vessel, a second portion 118 spaced apart from the processvessel, and a middle portion 122 between first portion 114 and secondportion 118. The circumference of the inner surface of first portion 114of gland housing 18 is greater than the circumference of the innersurface of middle portion 122 of gland housing 18. The circumference ofthe inner surface of middle portion 122 of gland housing 18 is greaterthan the circumference of the inner surface of the second portion 118 ofgland housing 18. In effect, gland housing 18 and wall 30 of the processvessel define a recess adjacent wall 30 of the process vessel and glandhousing 18 includes an inwardly extending projection formed by thesecond portion 118 of gland housing 18. A dovetail recess 124 is formedat the corner of gland housing 18 between the inner surface of glandhousing 18 and the radially extending end surface of gland housing 18.

Gland housing 18 defines a hole or channel 92 extending from a port 96in the outer surface of gland housing 18 to an opening 100. Channel 92and port 96 provide fluid communication from the outer surface of glandhousing to interior cavity 20 defined by gland housing 18. Channel 92and port 96 are noted using dashed lines because they are offset fromthe plane of the cross-section. In this embodiment, channel 92 and port96 are defined by second portion 118 of gland housing 18. Channel 92extends axially from port 96 to a radially extending surface 126 ofgland housing 18. Gland housing 18 can be formed (e.g., machined) out ofdurable structurally stable materials such as stainless steels and othermetals and alloys. Gland housing 18 also defines a recess 128 inradially extending surface 126 of gland housing 18. A seal (e.g., ano-ring 146) disposed in recess 128 engages gland housing 18 and sealingelement 38. O-ring 146 provides sealing contact to limit (e.g., prevent)flow of barrier fluid from barrier fluid cavity to the atmosphere.

A groove 90 machined in the outer surface of gland housing 18 receivesprojection 86 of housing clamp 14. Engagement between groove 90 of glandhousing 18 and projection 86 of housing clamp 14 sets the position ofgland housing 18. Housing clamp 14 compresses gland housing 18 againstwall 30 of the process vessel such that movement of gland housing 18 islimited (e.g., prevented) under normal operating conditions. In thisembodiment, groove 90 is defined by middle portion 122 of gland housing18.

A threaded bore 102 and counter-bore 106 are formed extending from theexterior surface to the interior surface of gland housing 18. A pin 110threaded into and through bore 102 extends into the interior cavity 20of gland housing 18. In this embodiment, bore 102 and counter-bore 106are defined by middle portion 122 of gland housing 18. Adapter 46includes a first portion 130 adjacent wall 30 of the process vessel anda second portion 134 spaced apart from wall 30 of the process vessel.The circumference of the inner surface of first portion 130 of adapter46 is less than the circumference of the inner surface of second portion134 of adapter 46. In effect, first portion 130 of adapter 46 extendsradially inward relative to second portion 134 of adapter 46. Thecircumference of the outer surface of first portion 130 of adapter 46 isslightly less than the circumference of the inner surface of firstportion 114 of gland housing 18, the circumference of the outer surfaceof second portion 134 of adapter 46 is slightly less than thecircumference of the inner surface of middle portion 122 of glandhousing 18, and the axial extent of first portion 130 of adapter 46matches the axial extent of first portion 114 of gland seal 18 such thatadapter 46 nests within gland seal 18. Adapter 46 can be formed (e.g.,molded or machined) of a non-corrosive material such as, for example, afluoropolymer (e.g., Teflon™) or a thermoplastic. A groove 138 definedin the outer surface of first portion 130 of adapter 46 is sized toreceive a seal (e.g., o-ring 146). Recess 138 is located oppositedovetail recess 124 in gland housing 18 and opens both outward towardsgland housing 18 and laterally towards wall 30 of the process vessel. Ano-ring 146 disposed in recess 138 engages both wall 30 and the innersurface of gland housing 18 as well as adapter 46. Some embodiments maybe implemented with seals other than o-rings (e.g., gaskets or injectedmoldable compounds).

A circumferential groove 142 is also defined in the outer surface ofadapter 46. Groove 142 is aligned with pairs of holes (not shown)extending through gland housing 18 (e.g., disposed extending parallel toa line tangent to the outer surface of gland housing 18 and extendingacross a small arc (5-10 degrees) of the circumference of the outersurface of adapter 46). Pins 148 inserted through the holes (not shown)in gland housing engage groove 142 to maintain the position of adapter46 relative to gland housing 18.

Another recess 150 sized to receive a seal is defined in the outersurface of second portion 134 of adapter 46. Another o-ring 146 disposedin recess 150 engages the inner surface of gland housing 18 and adapter46. Recess 150 is in fluid communication with barrier fluid cavity 50(e.g., through gaps between the inner surface of gland housing 18 andthe outer surfaces of adapter 46 and balancing element 42). Thus,barrier fluid pressure is applied to the right or “barrier” side ofo-ring 146 in recess 150. [As used herein, “right” and “left” indicatedirections with respect to the drawing being discussed and are used forease of description rather than to imply any absolute orientation.]

Balancing element 42 includes a first portion 154, a second portion 158,and a middle portion 162. The circumferences of the outer surfaces offirst portion 154, second portion 158, and middle portion 162 ofbalancing element 42 are, respectively, slightly less than thecircumferences of the inner surfaces of first portion 130 of adapter 46,middle portion 122 of gland housing 18, and second portion 134 ofadapter 46 such that balancing element 42 can nest within adapter 46 andgland housing 18. Balancing element 42 can move axially relative toadapter 46 and gland housing 18. Balancing element 42 can be formed(e.g., molded or machined) of a non-corrosive material such as, forexample, a fluoropolymer.

A biasing member or members (e.g., resilient coil springs 174) is/arepositioned between adapter 46 and balancing element 42. Coil springs 174are received within bores 178 defined extending axially within secondportion 158 of balancing element 42. Coil spring 172 engages a flat,radially-extending end surface of adapter 46. Coil springs 174 are sizedand configured such that, when seal 10 is assembled, coil springs 174are compressed and biases adapter 46 and balancing element 42 away fromeach other. Because adapter 46 is fixed in position, coil springs 174bias balancing element 42 towards sealing element 38. As described inmore detail below, the adapter-spring-balancing element combinationcompensates for the differential thermal expansion of sealing element 38relative to gland housing 18 and can maintain the engagement betweenseal components at a level sufficient to provide sealing contact whilepermitting radial motion of the sealing element 38. Some sealembodiments may be implemented using biasing or resilient members otherthan coil springs.

The outer surface of balancing element 42 extends radially outwardbetween the portions 154 and 162, as well as between portions 162 and158, of balancing element 42. Engagement between the radially extendingend surface of adapter 46 and the radially extending outer surface ofbalancing element 42 between second portion 158 and middle portion 162of balancing element 42 limits axial movement of balancing element 42towards wall 30 of the process vessel. The axial extent of first portion154 of balancing element 42 and the axial extent of second portion 134of adapter 46 are both greater than the axial extent of middle portion162 of balancing element 42. Thus, the outer surface of balancingelement 42 and the inner surface of adapter 46 define a seal cavity 166.

A seal (e.g., o-ring 146) disposed in seal cavity 166 engages the outersurface of balancing element 42 and the inner surface of adapter 46.Seal cavity 166 is in fluid communication with barrier fluid cavity 50and interior region 54 of the process vessel. Thus, barrier fluidpressure is applied to the right or barrier side of o-ring 146 andreaction fluid pressure is applied to the left or process side of o-ring146.

A recess 170 is defined in the end surface of second portion 158 ofbalancing element 42. Recess 170 is positioned slightly farther outwardthan the outer circumference of first portion 154 of balancing element42. A seal (e.g., o-ring 146) disposed in recess 170 engages balancingelement 42 and sealing element 38. Recess 170 can be in fluidcommunication with barrier fluid cavity 50 and interior region 54 of theprocess vessel. Some seal embodiments are implemented with other seals(e.g., opposed lip seals extending from balancing element 42) ratherthan the recess/o-ring combination.

The end surface of second portion 158 of balancing element 42 iscurved/slanted such that the axial extent of second portion 158 adjacentrecess 170 is greater than the axial extent of second portion 158 at theinner and outer surfaces of balancing element 42. This configuration canreduce the contact area, and thus friction, between balancing element 42and sealing element 38 as well as allow for some degree of angularmotion of sealing element 38.

Similarly, the inner surface of balancing element 42 includes a slanted(rather than radially extending) face at the transition between firstportion 154 and middle portion 162 of balancing element 42. The slantedface provides clearance for seal sleeve 26 relative to first portion 154of balancing element 42, the thickness of which provides structuralstability.

Sealing element 38 includes an axially extending body 182 supportinglips seals 186 and bearing projections 190 extending inwardly from body182. Circumferential lip seals 186 and bearing projections 190 areintegrally formed with body 182. (As used herein, “integrally formedwith” is used to indicate components that are parts of a unitary wholeas opposed to components that are attached to each other (e.g., byadhesive, mechanical joints, solder).) Sealing elements with integrallip seals can provide increased ease of manufacture and assembly,increased reliability, smaller size, and lower costs due to fewer partsrelative to sealing elements with discrete lips seals attached to aseparate body.

Sealing element 38 can be formed (e.g., molded or machined) of aresilient non-corrosive material with good sealing characteristics(e.g., a fluoropolymer or rubber) with circumferential lip seals 186extending inwardly from body 182 farther than bearing projections 190extend inwardly. When seal 10 is assembled, engagement with seal sleeve26 inclines lip seals 186 towards body 182 of sealing element 38. Lipsseals 186 are formed of a resilient material and the bias of lip seals186 towards their original orientations acts to maintain engagementbetween lip seals 186 and seal sleeve 26. When sealing element 182 isnot moving (e.g., when shaft 34 is centered), bearing projections 190are slightly spaced apart from seal sleeve 26.

The pair of lips seals 186 a closest to adapter 42 is bracketed by apair of bearing projections 190 that define a recess 194 in fluidcommunication with interior region 54 of the process vessel. Lip seals186 of lip seal pair 186 a, disposed with ends oriented towardsbalancing element 42, are activated by presence of a pressurizing fluidon the side away from the other lip seal pairs 186 b and 186 c, i.e. theprocess side. Two other pairs of lip seals 186 b and 186 c are bracketedby a pair of bearing projections 190 that define a recess 198. Lip sealsof lip seal pair 186 b are disposed with their ends oriented towards,i.e. opposing, lip seal pair 186 c, and lip seals of lip seal pair 186 care disposed with their ends oriented towards, i.e. opposing, lip sealpair 186 b. Lip seals of lip seal pairs 186 b and 186 c are activated bypresence of a pressurizing fluid applied between them. A channel (notshown) extending from the outer surface to the inner surface of sealingelement 38 provides fluid communication between barrier fluid cavity 50and recess 198 and opens into recess 198 between lip seal pair 186 b andlip seal pair 186 c. The multiple lip seal pairs 186 a, 186 b, and 186 ccan provide bi-directional sealing as discussed in more detail below.

A pin 110 is threaded into and through gland housing 18 into a bore 200defined in the outer surface of sealing element 38. Pin 110 preventsrotation of sealing element 38 relative to gland housing 18. However,bore 200 has sufficient radial extent to allow for radial movement ofsealing element 38 relative to gland housing 18.

As discussed above, seal sleeve 26 is held in place on shaft 34 by lockring 22. Seal sleeve 26 includes a projection 202 extending radiallyoutward to engage a mating recess 206 in lock ring 22. Two recesses 210defined in the inner surface of seal sleeve 26 receive seals (e.g.,o-rings 146). Recesses 210 are positioned such that o-rings engage thesurface of shaft 34 at two outwardly projections to provide a sealbetween shaft 34 and seal 10. The end of seal sleeve 26 oppositeprojection 202 is formed (e.g., molded or machined) to have a two-stagebeveled surface. The two stage beveled surface includes a first beveledsurface 212 disposed between the radially extending end surface 214 ofseal sleeve 26 and a second beveled surface 216. Second beveled surface216 is disposed between first beveled surface 212 and an axiallyextending outer surface 218 of seal sleeve 26. First beveled surface 212extends at an angle α₁ between 155 and 165 degrees relative to axiallyextending outer surface 218 of seal sleeve 26 and second beveled surface216 extends at an angle α₂ between 165 and 175 degrees relative toaxially extending outer surface 218 of seal sleeve 26. Seal sleeve 26can be formed (e.g., molded, machined) of a durable material such as,for example, a ceramic or metal with an oxide coating, e.g., chromium orother suitable material.

During assembly, gland housing 18 can be oriented with second portion118 of gland housing 18 at the bottom such that gravity will help holdthe various components in place. O-rings 146 can be installed as thevarious components are being assembled.

Seal 10 can be assembled by inserting sealing element 38 into interiorcavity 20 defined by gland housing 18. Bore 200 in sealing element canthen be aligned with bore 102 in gland housing and pin 110 threaded intobore 102 to extend into bore 200. Balancing element can then be insertedinto cavity 20 to rest on sealing element 38. Springs 174 can then beplaced in bores 178 in balancing element 42. Adapter 46 can then beplaced into cavity 20 to rest on springs 174 and/or balancing element42. Adapter 46 is then pressed towards sealing element 38 (compressingsprings 174) until pins 148 can be inserted through the holes (notshown) in gland housing to engage groove 142 to maintain the position ofadapter 46 relative to gland housing 18. The two halves of housing clamp14 are then placed in engagement with gland housing 18 and the assembledcomponents are bolted to wall 30 of the process vessel. Bolts 58 aretightened such that housing clamp 14 compresses gland housing 18 againstwall 30 of the process vessel. Seal sleeve 26 can be placed in positionon shaft 34 before the two halves of lock ring 22 are bolted together tohold seal sleeve 26 in position.

The shaft-seal sleeve-lock ring assembly can be inserted into engagementwith sealing element 38 before or after the other components areattached to wall 30 of the process vessel. The orientation of lip sealpairs 186 a and 186 c aids insertion of the shaft-seal sleeve-lock ringassembly because it is desired that these lip seal pairs 186 a and 186 cbend in the direction towards which force associated with the insertionprocess is applied. However, particular care must be taken as thechamfered end of seal sleeve 26 is inserted past lip seals 186 b becauseit is desired that the lip seals of lip seal pair 186 b bend in thedirection against which force associated with the insertion process isapplied. The lip seals of lip seal pair 186 b are formed extendinginwardly with a discrete bend towards the lip seals of lip seal pair 186c. As the shaft-seal sleeve-lock ring assembly is inserted, a firstbeveled surface 212 of the two stage beveled surface engages the ends ofthe lip seals of lip seal pair 186 b and starts to bend them from theirrest position towards the direction from which the seal sleeve 26 isbeing inserted (i.e. the barrier side). As engagement between the lipseals of lip seal pair 186 b and two stage beveled surface moves tosecond beveled surface 216, the lip seals are positioned in their“deflected” positions.

FIGS. 2A and 2B together illustrate the bidirectional sealing providedby seal 10. In use, port 96 of gland housing 18 is connected with asource of a pressurized barrier fluid. The barrier fluid fills barrierfluid cavity 50 and flows into seal cavity 166 (between balancingelement 42 and adapter 46) as well as recess 198 in sealing element 38.The barrier fluid applies an inward (or barrier side) force to sealingelement 38 that helps maintain sealing contact between sealing element38 and seal sleeve 26.

When the barrier fluid pressure is greater than the process pressure,there exists a positive pressure differential, and o-ring 146 in sealcavity 166 is urged towards the process side (leftwards in the drawing)as shown in FIG. 2A. The barrier fluid and process fluid are bothpresent on both ends of balancing element 42. However, as discussedabove, recess 170 is positioned at a slightly greater distance from theaxis than the outer circumference of first portion 154 of balancingelement 42. Thus, the barrier fluid pressure is applied to an area onthe process (left hand) side of balancing element 42 that is larger thanthe area on the barrier (right hand) side of balancing element 42, andthis positive pressure differential across the balancing element 42 ofthe barrier fluid pressure being relatively greater than the processfluid pressure urges the balancing element 42 towards sealing element38.

When the process pressure is relatively greater than the barrier fluidpressure (i.e. a negative pressure differential), O-ring 146 in sealcavity 166 is urged towards the barrier side (rightwards in the drawing)into sealing contact with balancing element 42 as shown in FIG. 2C.Thus, the process fluid pressure is applied to an area on the process(left hand) side of balancing element 42 that is relatively larger thanthe area on the barrier (right hand) side of balancing element 42. Thenegative pressure differential across the balancing element 42 of thebarrier fluid pressure being relatively less than the process fluidpressure still urges the balancing element 42 towards sealing element38.

Thus, the axial force on balancing element 42 is primarily due tosprings 174 which are been configured to maintain the engagement of theseals between sealing element 38 and both balancing element 42 and glandhousing 18 at a level sufficient to provide sealing contact whileallowing radial motion of sealing element 38.

The barrier fluid present between lip seal pair 186 b and lip seal pair186 c activates these seals. If the barrier fluid was in contact withlip seal pair 186 a when barrier fluid pressure is greater than processpressure (i.e. a positive pressure differential), the lip seals of lipseal pair 186 a would be inoperative. However, lip seal pair 186 bseparates lip seal pair 186 a from the barrier fluid. When the processpressure is greater than the barrier fluid pressure (i.e. a negativepressure differential), the primary seal between sealing element 38 inseal sleeve 26 is provided by the lip seals of lip seal pair 186 a whichare activated by the process fluid pressure.

FIGS. 3A and 3B together illustrate the operation of seal 10 tocompensate for radial motion of shaft 34. FIG. 3A shows the position ofsealing element 38 when shaft 34 is off-center relative to seal 10(downwards relative to the portion of the seal shown). Before radialmotion of shaft 34, lips seals 186 are in effective contact with sealsleeve 26 but bearing projections are spaced apart from seal sleeve 22.As shaft 34 and seal sleeve 26 move radially, lip seals 186 bend, andseal sleeve 26 contacts bearing projections 190. Force applied by sealsleeve 26 to bearing projections 190 causes sealing element 38 to followthe radial motion with sealing element riding outward as shown in FIG.3B. Without projections 190, lip seals 186 would be deflected further tocompensate for radial motion of shaft 34. Projections 190 can limit theamount that lip seals 186 bend such that lip seals 186 remain withintheir elastic range of deformation.

FIGS. 4A and 4B together illustrate the operation of seal 10 tocompensate for thermal effects on sealing element 38. The compensationfor radial motion of shaft 34 described above with reference to FIGS. 3Aand 3B is enabled in part by maintenance of a specific degree ofengagement between the seal components, such that the engagement issufficient to provide sealing between sealing element 38 and adjacentcomponents, and yet less than the amount of engagement that would fixsealing element 38 in place and restrict radial motion. It is desirableto form sealing element 38 with integral lip seals 186 of a resilientnon-corrosive material (e.g., a fluoropolymer or rubber). It isdesirable to form the seal housing (e.g., housing clamp 14 and glandseal 18) from durable, structurally stable materials (e.g., stainlesssteel). However, sealing elements 38 formed of material appropriate tomake integral lip seals 186 can exhibit differential thermal expansionof sealing element 38 relative to gland housing 18. Due to theelongated, narrow configuration of sealing element 38, such differentialthermal effect are primarily exhibited as relative axial expansion andcontraction. For example, sealing element 38 can have an initial lengthof L₁ as shaft 34 begins to rotate (see FIG. 4A). Heat caused byoperation of the process vessel and shaft rotation can cause sealingelement to axially expand to have a relatively greater length L₂ (seeFIG. 4B). As this lengthening occurs, balancing element 42 moves axiallyin the process direction (leftwards in the drawings) to compensate. Theaxial movement of balancing element 42 can maintain sufficientengagement to provide sealing contact between sealing element 38 andadjacent components while still allowing radial motion of sealingelement 38 to compensate for radial motion of shaft 34.

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention. Forexample, in some embodiments, adapter 46 is integrally formed as part ofgland housing 18 rather than being a separate element of the seal 10. Inanother example, seals as shown can be used in other applicationsincluding, e.g., for sealing of reaction vessels, mixing vessels, pumps,etc. In another example, in some embodiments, other resilient members(e.g., belleville washers, wave springs, etc) can be used in place ofthe springs 174/bores 178 combination to bias balancing element 42towards sealing element 38.

Accordingly, other embodiments are within the scope of the followingclaims.

1. A seal assembly configured to extend circumferentially about a shaft,the seal comprising: a housing defining an interior cavity open towardsa central axis of the seal; a sealing element configured to moveradially within the interior cavity in a manner to maintain sealingcontact, the sealing element disposed within the interior cavity of thehousing; a first seal disposed between the sealing element and thehousing, the first seal maintaining sealing contact to limit fluid flowbetween the sealing element and the housing; a first element configuredto move axially within the interior cavity in a manner to maintainsealing contact, the first element disposed within the interior cavityof the housing; a second element disposed between the first element andthe housing; a second seal disposed between the first element and thesealing element, the second seal maintaining sealing contact to limitfluid flow between the sealing element and the first element duringradial motion of the sealing element relative to the first element; abiasing member disposed in contact with the first element, the biasingmember configured to bias the first element towards sealing contact withthe sealing element such that first element and the second seal maintainsealing contact during axial movement of an end face of the sealingelement; and a third seal disposed between the first element and thehousing, the third seal maintaining sealing contact to limit fluid flowbetween the housing and the first element, wherein the third seal isdisposed in a third seal cavity mutually defined by the first elementand the second element.
 2. The seal assembly of claim 1, wherein thethird seal is disposed to limit fluid flow between a first portion ofthe cavity in fluid communication with a first fluid reservoir at afirst pressure and a second portion of the cavity in fluid communicationwith a second fluid reservoir at a second pressure.
 3. The seal assemblyof claim 2, wherein a pressure differential between the first pressureand the second pressure, taken across the third seal, biases the firstelement towards the sealing element when the first pressure isrelatively greater and biases the first element towards the sealingelement when the second pressure is relatively greater.
 4. The sealassembly of claim 2, wherein the third seal is operable to move axiallyin the third seal cavity in response to a pressure differential betweenthe first pressure and the second pressure.
 5. The seal assembly ofclaim 4, wherein the third seal is operable to move axially in the thirdseal cavity in response to the pressure differential, the third sealbeing urged toward a first position when the first pressure isrelatively greater and toward a second position when the first pressureis relatively less.
 6. The seal assembly of claim 4, wherein the thirdseal comprises an o-ring.
 7. A seal assembly configured to extendcircumferentially about a shaft, the seal comprising: a housing definingan interior cavity open towards a central axis of the seal; a sealingelement configured to move radially within the interior cavity in amanner to maintain sealing contact, the sealing element disposed withinthe interior cavity of the housing; a first seal disposed between thesealing element and the housing, the first seal maintaining sealingcontact to limit fluid flow between the sealing element and the housing;a first element configured to move axially within the interior cavity ina manner to maintain sealing contact, the first element disposed withinthe interior cavity of the housing; a second seal disposed between thefirst element and the sealing element, the second seal maintainingsealing contact to limit fluid flow between the sealing element and thefirst element during radial motion of the sealing element relative tothe first element; a biasing member disposed in contact with the firstelement, the biasing member configured to bias the first element towardssealing contact with the sealing element such that first element and thesecond seal maintain sealing contact during axial movement of an endface of the sealing element; and a third seal disposed between the firstelement and the housing, the third seal maintaining sealing contact tolimit fluid flow between the housing and the first element wherein thesealing element comprises: a sealing element body; a plurality of firstland protrusions integrally formed with and extending from the sealingelement body; and a plurality of second lip protrusions integrallyformed with and extending from the sealing element body; wherein thesecond lip protrusions are biased towards a position in which the secondlip protrusions extend relatively further from the body than the firstland protrusions.
 8. The seal assembly of claim 7, wherein each secondprotrusion defines a resilient ridge positioned for deflection bycontact with an annular member inserted into the sealing member.
 9. Theseal assembly of claim 8, wherein the second lip protrusions arearranged in pairs with a first pair of the second lip protrusions havingtips deflected towards a second pair of the second lip protrusions, thesecond pair of protrusions having tips deflected towards the first pairof the second lip protrusions, and a third pair of second lipprotrusions having tips deflected away from the first pair and secondpair of second lip protrusions.
 10. The seal assembly of claim 8,wherein a first end of the annular member defines a first beveledsurface disposed between a radially extending end surface of the annularmember and a second beveled surface, the second beveled surface disposedbetween the first beveled surface and an axially extending outer surfaceof the annular member.
 11. The seal assembly of claim 10, wherein thefirst beveled surface extends at an angle between 155 and 165 degreesrelative to the axially extending outer surface of the annular memberand the second beveled surface extends at an angle between 165 and 175degrees relative to the axially extending outer surface of the annularmember.
 12. The seal assembly of claim 7, wherein the first landprotrusions are relatively less flexible than the second lipprotrusions.
 13. The seal assembly of claim 1, further comprising a pinextending from the housing into a bore defined in the sealing element tolimit rotation of the sealing element relative to the housing whileallowing radial motion of the sealing element within the housing. 14.The seal assembly of claim 1, wherein the seal comprises a split seal.15. The seal assembly of claim 1 wherein the sealing element comprises:a sealing element body; a plurality of first land protrusions integrallyformed with and extending from the sealing element body; and a pluralityof second lip protrusions integrally formed with and extending from thesealing element body, the second lip protrusions being biased towards aposition to extend relatively further from the sealing element body thanthe first land protrusions.
 16. The seal assembly of claim 15, whereineach of the second lip protrusions defines a resilient ridge, positionedfor deflection by contact with an annular member inserted into thesealing member.
 17. The seal assembly of claim 16, wherein the secondlip protrusions are arranged in pairs with a first pair of the secondlip protrusions having tips deflected towards a second pair of thesecond lip protrusions, the second pair of second lip protrusions havingtips deflected towards the first pair of the second lip protrusions, anda third pair of second lip protrusions having tips deflected away fromthe first pair and the second pair of second lip protrusions.
 18. Theseal assembly of claim 15, further comprising a pin extending from thehousing into a bore defined in the sealing element to limit rotation ofthe sealing element relative to the housing while allowing radial motionof the sealing element within the housing.